SynScan V2 Instruction Manual page 17

Generally speaking the SynScan
However, if higher precision is required, for example for astro-photography, accurate polar alignment and
"cone" error calibration may be required. See the manual for HEQ5/EQ6 mount for information on accurate
polar alignment using the polarscope.
"Cone" error is a common inaccuracy found on all German equatorial mounts. It is a result from the optical
axis not being aligned to the R.A. axis of the mount. This affects the pointing accuracy of the SynScan
Three-Star Alignment automatically compensates for the "Cone" error. If you choose One-Star or Two-Star
Alignment method, you will need to perform manual mount calibration to eliminate the "cone" error. The
following calibration procedure should be performed before the initial use of the telescope and periodically
thereafter to ensure the accuracy.
Testing for Cone Error
This test is done at night using two bright stars located on the opposite side of the sky. Make sure the
telescope is properly polar-aligned using the polarscope. Perform the One-star Alignment using an eastern
star as the alignment star (see One-star Alignment). After the star alignment, choose a bright star on the
western sky from the SynScan
is perfectly aligned to the R.A. axis, the telescope will accurately put the star in the center of the eyepiece.
In this case, there is no "cone" error in your telescope setup and you will not need to perform the
calibration. It is acceptable if the star is slightly off-center as long as it is in the eyepeiece view and close to
the center. Many factors determine the pointing accuracy of the SynScan
alignment, R.A. or Dec lock knob being loose, or "cone" error. If your telescope puts the star outside the
eyepiece view, you need to first determine whether it is "cone" error that causes the pointing inaccuracy. To
find out, simply move the telescope in R.A. axis by pressing the Left or Right direction key. If the star can
be moved into the eyepiece view without adjusting the Dec axis, it is likely that "cone" error exists in your
telescope setup.
Calibration Procedure
1.
Insert the illuminated reticle eyepiece. Make sure that the telescope is properly set up and balanced, and
the finderscope is perfectly aligned with the telescope tube.
Step 2 to 4 is to identify R.A. and Dec movements
in the reticle eyepiece. If you are already familiar
with the movements, you may skip to step 5.
2.
Find any bright star and place it in the center of the
eyepiece view.
3.
Look into the eyepiece. Move the telescope in R.A.
axis using the R.A. direction keys on the hand control
while carefully observing the movement of the star.
4. Keep moving the the telescope in R.A. axis back and
forth to keep the star within the eyepiece view. Rotate
the eyepiece until the movement of the star becomes
parallel to (or matches) any set of the lines (Fig.A-1).
This set of lines will represent R.A. movement in the
course of this procedure, and the perpendicular lines
will represent Dec movement. Tigten the set screws
to secure the eyepiece in place. Make sure that the
eyepiece will remain stationary when the telescope is
being rotated.
5.
Point the telescope to North and set the latitude scale
to your local latitude using the altitude adjustment T-
bolts, or place Polaris on the crosshair of the
polarscope if your polarscope is perfectly aligned with
the rotation axis of the mount.
produces pointing and tracking accuracies adaquate for most applications.
TM
object database and have the telescope slew to the star. If the optical axis
TM
I
, for example incorrect star
TM,
Required accessory: Illuminated
reticle eyepiece with double
crossline pattern. Depending on the
design of your mounting plate
(dovetail bar), modifications may
be required. (See step 10 for the
required mechanism
mounting plate.)
Fig.A-1
movement
of the star
eyepiece view
.
TM
on the
rotate eyepiece
this way